[travisp]

Yet nearly every controlled trial supplementing Vitamin D has limited or no effect, except maybe in the most deficient people. Many many trials have been conducted. Vitamin D advocates always have an excuse — it’s too little vitamin D; no, actually you also have to add Vitamin K2; etc

Part of the problem of all the observational trials looking at vitamin d is that low vitamin d is a biomarker for being less healthy. People who are ill spend less time outdoors. People who spend more time outdoors are already healthier and are also getting other benefits from their outdoor activities.

You can try to control for all of these things, but every time we actually try to test what happens if you give people Vitamin D, we find almost no benefit.

[karmajunkie]

Well, I can tell you that I'm on a vitamin D supplement and there's very definitely a direct benefit to it treating early osteomalacia.

[travisp]

Yes, rickets and osteomalacia (when caused by vitamin d deficiency) are both treatable with vitamin d. Randomized controlled trials clearly show this, unlike the vitamin d trials for most other things that people are pushing vitamin d for.

Everyone should probably have their blood level of vitamin d tested. Most people are not going to see dramatic changes to health from vitamin d supplementation.